By 121 b.c., Rome had acquired S Transalpine Gaul, and by the time of Julius Caesar it had been pacified. It was usually called the Province (Provincia, hence modern Provence), and it included a strip 100 mi (160 km) wide along the sea from the E Pyrenees northeastward and up the Rhone valley nearly to Lyons. Julius Caesar conquered Gaul in the Gallic Wars (58 b.c.-51 b.c.). He is the best ancient source on Gaul, and he has immortalized its three ethnic divisions, Aquitania (S of the Garonne), Celtic Gaul (modern central France), and Belgica (very roughly Belgium). Aquitania was probably inhabited by the ancestors of the Basques, and the Belgae were probably Celts, like the rest of the Gauls.

On the basis of these distinctions, Augustus in 27 b.c. set up great administrative divisions: Narbonensis (the old Province), under the direct rule of the Roman senate; Aquitania, now extending from the Pyrenees to the Loire; Lugdunensis (Celtic Gaul), a central strip mainly between the Loire and the Seine; and Belgica, including most of the rest. The latter three provinces were administered from Lugdunum (now Lyons), capital of Lugdunensis. Upper and Lower Germany were taken from Gaul; these included the upper Rhine, Alsace, W Switzerland, the Franche-Comté, E Belgium, S Netherlands, and the Rhineland.

In Roman Gaul it often became customary to call the chief center of a tribe or the country around it by some form of the tribe's name. Many of these names survive today. The principal tribes of Gaul (with the modern survivals or locations) were: Abrincati (Avranches); Aedui; Allobroges; Ambiani (Amiens); Andecavi (Angers, Anjou); Atrebates (Arras); Baiocassi (Bayeux); Bellovaci (Beauvais); Bituriges (Bourges, Berry); Cadurci (Cahors, Quercy); Carnutes (Chartres); Catalauni (Châlons); Cenomani (Le Mans, Maine); Eburovici (Évreux); Helvetii; Lemovices (Limoges, Limousin); Lingones (Langres); Lexovii (Lisieux); Meldae (Meaux); Namnetes (Nantes); Nervii; Parisii (Paris); Petrocorii (Périgueux, Périgord); Pictones or Pictavi (Poitiers, Poitou); Redones (Rennes, Breton Roazon); Remi (Reims); Ruteni (Rodez); Santones (Saintes); Senones (Sens); Sequani, in the Franche-Comté; Silvanecti (Senlis); Suessiones (Soissons); Treveri (Trier, French Trèves); Tricassi (Troyes); Turones (Tours, Touraine); Veneti (Vannes, Breton Gwened).

Although the Romans had won political control over Gaul, they never succeeded in imposing Roman culture throughout the land. Various provinces differed greatly in the degree to which they accepted Roman culture. The only serious attempt to rebel politically against Rome was the uprising of Postumus (a.d. 257), but Gallo-Roman civilization was too strong to fall before anything but the Germans of the 5th and 6th cent.

The villa system spread (see feudalism). A landed aristocracy grew up, employing the laborers, who made up the principal part of the population. The influence of Christianity and the ravages of Germanic invaders forwarded the local organization around the cities. The greatest testimony to the stability and thoroughness of the culture of Roman Gaul is the survival of the Latin language as French. However, an indication of regionalism is that Provençal, also a Romance language, survived in S France for centuries. For history see France.